Soy polysaccharide (soy fiber) is produced in large quantities as a byproduct of protein and oil isolation during soybean processing. This carbohydrate byproduct, which is commonly referred to as soy spent flakes or soy fiber, is composed primarily of water-insoluble cell wall polysaccharides. Although the polysaccharide components of this material obtained from some isolation processes can make up over 80% of its dry matter, limited knowledge exists of the exact structure and linkages of these carbohydrates. Structural analyses have indicated that soy polysaccharide is composed primarily of various monosaccharides including galactose, glucose, arabinose, galacturonic acid, xylose, rhamnose and fucose (Aspinall et al., J. Chem. Soc. C(0), 1065-1070). Also, it has been shown that soy polysaccharide contains spans of certain polysaccharide, such as galacturonans, rhamnogalacturonans, arabinogalactans and arabinans (FIG. 1).
Soy polysaccharide is generally insoluble in many types of solvents, including water. For this reason, recent studies on this type of polysaccharide have focused on either chemical extraction alone (Li et al., Molecules 17:753-761) or in combination with enzymatic hydrolysis (Yamaguchi et al., Carbohydrate Polymers 30:265-273) to solubilize the polysaccharide for structural analysis. These types of solubilization techniques have made soy polysaccharide more accessible to structural analysis techniques (e.g., NMR, SEC).
Despite these advances, development of new techniques for solubilizing soy polysaccharides could be beneficial. Solubilized soy polysaccharides produced by alternative means, such as those now disclosed herein, have potential utility in various applications.